The present invention relates to a bearing for use in high speed operation under high-temperature and, mud and water splashing conditions.
Bearings for use in automobiles, such as, for example, propeller-shaft support center bearings, drive-shaft center bearings, wheel bearings, alternator bearings, and bearings for an auxiliary device, are required to withstand high-speed and high-temperature conditions and also to have high anti-mud and sealing properties.
One typical prior-art bearing of this kind is shown in FIG. 3. Such bearings comprise a plurality of balls 3 arranged in circumferentially spaced apart relation between an inner ring 1 and an outer ring 2, a ring shaped outer seal member 6 having an inner circumferential portion 6a fitted in a support groove 4 of the inner ring 1 and an outer circumferential portion 6b held in slide contact with an inner periphery 2a of the outer ring 2, and a ring shaped inner seal member 7 having an outer circumferential portion 7a fitted in a support groove 5 of the outer ring 2 and an inner circumferential portion 7b held in slide contact with an outer periphery 1a of the inner ring 1. A kind of grease G.sub.1 e.g., a heat-resistant grease, is contained in a space 8 defined between the outer seal member 6 and the inner seal member 7 and also in a space 9 defined in cooperation with the balls 3, the inner seal member 7 and the inner and outer rings 1, 2.
Because of the heat resistant grease G.sub.1 contained in the space 8 between the outer seal member 6 and the inner seal member 7 and in the space 9 inward of the inner seal member 7, however, such conventional bearing has a drawback that it is not well resistant to water and corrosion; if water, mud, or the like from an external source deposits on the slide contact portion between the outer circumferential portion 6b of the outer seal member 6 and the inner periphery 2a of the outer ring 2, pitting is likely to develop on the slide contact portion, the outer circumferential portion 6b of the outer seal member 6 being thus deteriorated in sealing properties, which fact in turn leads to deterioration of the inner seal member 7 in water resistance.
In the present state of the art, there is no grease well qualified to meet the heat resistance requirements on one hand and the water-resistant and corrosion-preventive requirements on the other hand.